An image, for example from a digital camera, is constituted by a set of N×M pixels, where N is the height of the image in pixels and M the width of the image. The image so obtained is encoded and compressed before being stored in memory. The initial data, that is to say the information representing the pixels of the image, are organized in a bidirectional array, that is for example accessible row by row.
It is known that the decoding of digital images requires a relatively high memory capacity as well as a long processing time.
For this reason, numerous studies have been made over several years with the object of rapidly and advantageously accessing a part of the image and only to decode the region of the image to be accessed.
For example, in the case in which a user wishes to access a region of an image, it is desirable to be able to access solely that portion of the encoded image, which means that only the region selected by the user must be decoded.
For this, a method is known of randomly accessing a file while keeping up to date a list of offsets, as described in the state of the art according to the following reference: http://megara.ee.nctu.edu.tw/course/PL03/Ch14.pdf.
This list makes it possible to access different parts of a file in jumps without having to sequentially go through the entirety of the data of the file.
Similarly, in the JPEG2000 specification, with reference to the following address, http://www.ee.unsw.edu.au/˜taubman/publications_files/remote-browsing-icip02.pdf, it is also possible to randomly access an image.
The drawback of these approaches is due to the fact that the writing of the offset information, that is to say the information making it possible to go through the file, during the phase of encoding the image, is an inappropriate process for continuous processing. This is because it requires the interruption of the process of writing the encoded file in order to write the offset information.
The object of the present invention is to remedy at least one of the aforementioned drawbacks by providing a linear encoding method which can in particular make it possible to work without saving to memory and a method for accessing a region of an encoded image and the associated devices.